Dual chamber and gear pump assembly for a high pressure delivery system

ABSTRACT

A high pressure delivery device for delivering a medicament includes a first chamber for storing a supply of the medicament and a second chamber in fluid communication with the first chamber. A fluid connection path is in fluid communication with the second chamber for administering the medicament. A valving system is in fluid communication with the first chamber, the second chamber and the fluid connection path. The valving system allows a dose of the medicament to be injected from the first chamber into the second chamber while substantially preventing backflow of the dose into the first chamber and substantially preventing leakage through the fluid connection path. The valving system also allows the dose in the second chamber to be administered through the fluid connection path while substantially preventing the dose from flowing back into the first chamber.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of non-provisional application Ser.No. 12/737,447, filed Apr. 7, 2011, which is the U.S. national stageunder 35 U.S.C. § 371 of International Application No.PCT/US2009/004132, filed Jul. 17, 2009, which claims the benefit under35 U.S.C. § 119(e) of provisional application Ser. No. 61/082,053, filedJul. 18, 2008, the entire disclosures of all of said prior applicationsbeing hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a high pressure delivery system fordelivering a medicament. More particularly, the present inventionrelates to a high pressure drug delivery system that diverts highpressures away from the drug storing chamber to prevent medicationleakage and inaccurate doses.

BACKGROUND OF THE INVENTION

In certain circumstances, it is desirable to inject medication directlyinto human tissue. Typically, syringes are used to inject medicamentsinto tissue areas, such as the intramuscular tissue layer, thesubcutaneous tissue layer, and the intradermal tissue layer. Each ofthese tissue layers has specific characteristics that affect the amountof fluid pressure needed to inject a fluid into the targeted tissuelayer. When injecting fluids into each of these tissue layers, the usermust exert enough force on the injection device to overcome differentamounts of backpressure associated with the particular tissue layer. Ingeneral, practitioners and self-injectors, such as diabetics, arefamiliar with the force necessary to inject fluids into the subcutaneouslayer. Injections into the subcutaneous and intramuscular tissue layerscan cause discomfort to the patient or self-injector because of thecharacteristics of the tissue, needle length and needle diameter orgauge. It is desirable to employ shorter, smaller gauge needles toachieve delivery into the intradermal tissue layer.

It is noted that when the needle lengths are shortened and needlediameters are made smaller, the fluid dynamics of the injection devicechanges. Additionally, the fluid dynamics between the injection deviceand the targeted tissue layer also change because the shorter needlelength injects the fluid into a different tissue layer, such as theintradermal layer. Since the tissue density between the intramuscular,subcutaneous, and intradermal tissue layers varies, the ease with whichfluid may be injected into each type of tissue layer varies. Thevariation in tissue density causes changes in the backpressure exertedby the tissue against the fluid when it is injected. For instance, thebackpressure associated with the intradermal tissue layer is greaterthan the backpressure associated with the subcutaneous tissue layer,thereby requiring a higher pressure and a greater force to accomplishthe injection.

Currently, several pen injection systems are commercially available forsubcutaneous substance delivery of medication. These pen injectionsystems typically use 29 to 31 gauge needles having lengths of between 5mm and 12.7 mm, and are used to deliver the contents of a medicamentcartridge, such as insulin, to the subcutaneous tissue layers of apatient rapidly and conveniently. The medicament cartridges aregenerally of a standard volume and size (including a fixed crosssectional area). The pressure of delivery is the quotient of theactuation force exerted by a user and the cross sectional area of thecartridge. Since the cross-sectional area of the cartridge is fixed,higher delivery pressures require higher actuation forces by the user.

A “microneedle” pen system has been developed to facilitate subcutaneoussubstance delivery. Such “microneedle” drug delivery systems may includeshorter needles, typically less than or equal to 3 mm, with smallerdiameters, in the range of 30 to 34 gauge or thinner. Such needle lengthand gauge size combinations are desirable to provide for sharp, yetshort, point geometries that can more accurately target substancedelivery to only certain selected tissue, such as the deep intradermalor shallow subcutaneous tissue layers, thereby permitting controlledfluid delivery. Current typical pen injection systems used forsubcutaneous delivery are not believed optimal for use by the generalpopulation of self-injectors for delivery into the intradermal layerbecause of, inter alfa, the high backpressures associated with injectingfluid into the intradermal layers of the skin using microneedles.

To achieve effective medication delivery to the targeted tissue layer inlight of higher backpressures, it is desirable to control two factors:the depth accuracy of the injection and the rate of the injection. Thisis of particular interest in connection with intradermal injectionsbecause the backpressures are relatively high, but similar analysis canbe applied when injecting into the intramuscular or the subcutaneoustissue layers. The delivery of medicament within the narrow depth rangeof the intradermal tissue layer should first be assured, and maintainedduring injection. Once the depth accuracy is obtained, the rate ofinjection should be controlled to minimize or eliminate leakage of themedicament into other tissue layers or back out through the skin.Additional details of intradermal drug delivery and microneedles havebeen previously described in U.S. Pat. No. 6,494,865, issued on Dec. 17,2002, U.S. Pat. No. 6,569,143, issued on May 27, 2003, PCT PublicationNo. WO2005025641, published Mar. 24, 2005, and U.S. Patent ApplicationPublication No. 2005/0065472, published on Mar. 24, 2005, all of whichare assigned to Becton, Dickinson and Company, and the entire content ofeach such patent and application being incorporated herein by reference.

The intradermal tissue layer of the skin is considerably denser than thesubcutaneous tissue region. The density of the intradermal tissue layeron a particular patient is, in part, a function of their collagenmake-up, which is affected by the patient's age, and the location of theinjection site on the patient's body. This increased density of theintradermal tissue layer can create a greater backpressure resistance onthe injection device than the resistance created when injecting into thesubcutaneous tissue region. To overcome the increased backpressureresistance when injecting into the intradermal tissue layer with aconventional drug delivery pen, the user or patient would need to exertgreater actuation force (which could be substantial) on the injectordevice actuator or employ some sort of powered injector device. In theseapplications, the injector device must be designed to withstand thegreater backpressure from the intradermal injection site as well as theadditional force exerted by the user or patient. Further, the increasedactuation force required to actuate the injector device may result inthe fluid “jetting” past the desired tissue depth due to the increasedfluid pressure.

Conventional drug delivery pens may require that the user keep theneedle seated in the skin for a period of up to about 10 seconds, afterthe injection has been completed, to allow for the “axial compliance” ofthe pen mechanism (or lead screw) and the cartridge back-end stopper toequilibrate to minimize “drool” from the needle tip upon withdrawal.Such time periods may need to be increased to accommodate any additionalaxial compliance resulting from higher backpressures, and such increasedtime periods can also decrease the required force to make the injection.

As advances in understanding the delivery of drug proceeds, the use ofintradermal delivery systems is expected to increase. Use of a“standard” length needle to deliver a drug substance intradermally hasits shortcomings, as noted above. It is not possible to use a deliverydevice having a needle length suited for intradermal injection toaspirate a syringe with drug substance from a multi-use vial. Thus,there are shortcomings in the prior art that prevent administering anintradermal injection using a “standard” length needle and a multi-usevial. It would be advantageous to have a drug delivery device capable ofaccessing substances stored in multi-dose vials and delivering suchsubstances into the intradermal region of the skin without encounteringthe shortcomings described above.

Existing drug delivery pens offer several advantages over syringe basedsystems for delivering insulin subcutaneously. Reusable drug deliverypens hold 20 or more doses without requiring the drug cartridge to berefilled. Dose setting is achieved simply with the use of a dial.However, those drug delivery pens are designed for low pressuresubcutaneous injections. Intradermal injection of insulin and othermedications provides faster uptake of the drug, thereby leading toimproved therapy. Existing drug delivery pens have several limitationsregarding intradermal drug delivery. First, the mechanical advantageprovided by the pen is minimal and requires the user to supply upwardsof 20 lbs of force to generate sufficient pressure. Secondly, the pencomponents are often damaged by this high force, resulting in leakingand inaccuracy at the high pressures. Additionally, the size of the drugdelivery pen required to obtain the high pressures associated withintradermal drug delivery would be too large for a user to convenientlycarry.

There are no existing intradermal pen-like devices that take advantageof pen-like, dial-a-dose accuracy and ease of use with syringe like(small diameter) high pressure performance. Existing drug delivery pensrequire a large force to inject medication into the intradermal layer,thereby making the intradermal medication injection difficult.Furthermore, the drug delivery pen components are often damaged due tothe high pressures, thereby resulting in medication leakage and doseinaccuracy.

Therefore, a need exists to provide a system and method for enablingusers or patients to perform high pressure delivery of compounds, suchas therapeutic drugs, vaccines, and diagnostic materials, at acontrolled rate without requiring the exertion of an overly large forceor resulting in an unwieldy device.

SUMMARY OF THE INVENTION

In accordance with an aspect of the present invention, a high pressuredrug delivery system is provided that separates the dose settingmechanisms from the high pressure associated with drug delivery so thatthe stress caused by the high pressure does not affect the dose setting.

The accuracy of a pen's screw dose setting is combined with thehydraulic advantage of a small bore syringe to deliver medicaments inhigh pressure applications, such as an intradermal area. Valving betweenthe cartridge and the syringe operates like a plunger-type reciprocatingdevice with two check valves that allow flow into the syringe duringdose setting and only allows flow through the microneedle duringinjection. The check valve allows a user to inject the dose from thesyringe back into the cartridge when a user accidentally overdoses intothe syringe.

In accordance with another aspect of the present invention, a highpressure drug delivery system is provided that uses a gear pump assemblyto accomplish the high pressure drug delivery.

Other objects, advantages, and salient features of the invention willbecome apparent from the following detailed description, which, taken inconjunction with the annexed drawings, discloses exemplary embodimentsof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above benefits and other advantages of the various embodiments ofthe present invention will be more apparent from the following detaileddescription of exemplary embodiments of the present invention and fromthe accompanying figures, in which:

FIG. 1 is a schematic diagram of a dual chamber assembly for a highpressure delivery system having a 3-way valve according to an exemplaryembodiment of the present invention;

FIG. 2 is a schematic diagram of a dual chamber assembly for a highpressure delivery system having a 3-way valve and a vent according toanother exemplary embodiment of the present invention;

FIG. 3 is a schematic diagram of a dual chamber assembly for a highpressure delivery system having check valves according to anotherexemplary embodiment of the present invention;

FIG. 4 is a schematic diagram of a dual chamber assembly for a highpressure delivery system having check valves and a vent connected to oneof the chambers according to another exemplary embodiment of the presentinvention;

FIG. 5 is a schematic diagram of a dual chamber assembly for a highpressure delivery system having a plunger connected to both chambersaccording to another exemplary embodiment of the present invention;

FIG. 6 is a top view of the schematic diagram of FIG. 5 showing anexemplary arrangement of the plungers;

FIG. 7 is top view of the schematic diagram of FIG. 5 showing a plungerhaving a substantially T-shaped handle;

FIG. 8 is a schematic diagram of a dual chamber assembly for a highpressure delivery system according to another exemplary embodiment ofthe present invention;

FIG. 9 is a table of characteristics for a user input of four pounds;

FIG. 10 is a schematic diagram of a gear pump assembly for a highpressure delivery system according to an exemplary embodiment of thepresent invention;

FIG. 11 is a schematic diagram of an exemplary gear arrangement of thegear pump assembly of FIG. 10;

FIG. 12 is a schematic diagram of a gear pump assembly for a highpressure delivery system according to another exemplary embodiment ofthe present invention;

FIG. 13 is a schematic diagram of an exemplary syringe assembly of thehigh pressure delivery system of FIG. 12;

FIG. 14 is a perspective view of an exemplary gear pump assembly of thehigh pressure delivery system of FIGS. 10 and 12;

FIG. 15 is a graph of a constant rate dose delivery;

FIG. 16 is a table of the tooth position and the volume of the dosedispensed for the graph of FIG. 15;

FIG. 17 is a graph of a variable rate dose delivery; and

FIG. 18 is a table of the tooth position and the volume of the dosedispensed for the graph of FIG. 15.

Throughout the drawings, like reference numbers will be understood torefer to like parts, components and structures.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

An exemplary embodiment of the present invention includes a highpressure drug delivery system having a cartridge, which is preferably atypical 3 ml cartridge, coupled to a preferably disposable syringe thataccommodates the high pressure generated from a small diameter syringe.The cartridge and syringe are coupled by a valving system that allowsmedicament to flow from the cartridge to the syringe and then preventsbackflow during delivery of the medicament. The valving system mayinclude 3-way valves, stopcock valves, or check valves, or any othersuitable valve. The valving system prevents contamination of the storedmedicament, which is a greater concern due to the use of a dual chambersystem. An intradermal microneedle pen needle may be attached to thesyringe and replaced with each use, thereby providing an interchangeableneedle. The device may have a switch to allow the user to correct a dosewithout wasting the dose in the event that the dose is overdrawn.

To operate the high pressure drug delivery system, a user installs acartridge or vial if it is a reusable product. Alternatively, the highpressure drug delivery system may be preconnected and is completelydisposable. The user then sets or determines a dose, such as by dialing,in a manner similar to existing drug delivery pens. Depending on thevalving system used, the user may need to set the proper valve position.The user injects the dose into the syringe located adjacent the pencartridge or vial. As the dose enters the syringe, the plunger is pushedup. Alternatively, a single plunger may draw the dose into the syringe.A valving system allows flow from the cartridge or vial into theinjection chamber of the syringe but does not allow backflow unless theuser chooses to manually override the valve to allow backflow to resetor correct the dose. The user then connects any fluid connection path,such as microneedle, if it is not already connected. The fluidconnection path, i.e., the needle, is then primed. The fluid connectionpath is then inserted into the area where the drug is to be delivered,such as the microneedle into an intradermal area, and the user depressesthe syringe plunger to inject the dose.

In an exemplary embodiment of the present invention, the high pressuredrug delivery system uses a microneedle and existing syringe or syringecomponents to generate the high pressure (approximately 200 psi) neededfor intradermal delivery. The dose setting mechanism it separated fromthe high pressure so that the stress caused by the high pressure doesnot affect the dose setting. Existing dose setting/resetting mechanismsthat are proven accurate, as well as commercially available cartridges(e.g., 3 ml cartridges), may be used to provide accurate doses for bothsmall and large doses. Furthermore, the high pressure drug deliverysystem according to exemplary embodiments of the present invention mayuse conventional and completely disposable 3 ml cartridges with multiplemicroneedle pen needles, and may have a reusable dose setting (pen-like)and a valving system with a disposable syringe (using multiplemicroneedle pen needles) allowing for user installation of 3 mlcartridges. By using disposable parts, the high pressure drug deliverysystem is efficient and inexpensive.

An automatic priming feature allows the user to set the dose as inexisting drug delivery pens, but also includes in the dose a primingdose. When the dose (dose plus priming dose) is transferred to thesyringe, which is a limiting syringe that only allows the volume for theexact dose, the prime dose has nowhere to go but through a check valveand out through the fluid connection path, such as a needle, therebyautomatically priming the high pressure drug delivery system.

FIGS. 1-4 are schematic diagrams of exemplary embodiments of highpressure drug delivery systems. As shown in FIGS. 1 and 5, the highpressure drug delivery system 100 includes a first chamber 111, a secondchamber 121, a valving system 131 and a fluid connection path 141. Thefirst chamber 111 may be a conventional 3 ml cartridge that stores themedicament to be delivered. Conventional 3 ml cartridges hold twenty(20) doses (15 unit average). The second chamber 121 may be aconventional syringe with a plunger 123. The fluid communication path141 may be a disposable microneedle. The valving system 131 may be a3-way valve in fluid communication with the first chamber 111, thesecond chamber 121 and the fluid communication path 141.

To use the high pressure drug delivery system 100 of FIGS. 1 and 5, theuser sets the 3-way valve to the dose setting. The dose is then dialedusing the thumbwheel of the cartridge and may be viewed through the dosewindow. The cartridge plunger 113 is then depressed to transfer the doseto the syringe, thereby causing the syringe plunger 123 to rise. Thevalve lever is then flipped to the inject setting. When the valve leveris in the inject setting, the valve prevents backflow of the dose to thecartridge. The user then uses the syringe plunger 123 to inject thedose. The valving system 131 prevents the first chamber 111 from seeingthe high pressure associated with the drug delivery, thereby preventingdose inaccuracies, leakage and other problems associated with cartridgesbeing exposed to high pressure.

As shown in FIG. 6, the handle of the cartridge plunger 113 may benested within the handle of the syringe plunger 123 to provide ergonomicoperation. As shown in FIG. 7, the syringe plunger 123 may have asubstantially T-shaped handle to increase the force acceptable to theuser's hand.

As shown in FIG. 2, the high pressure drug delivery system 200 includesa first chamber 211, a second chamber 221, a valving system 231 and afluid connection path 241. The first chamber 111 may be a conventional10 ml drug vial that stores the medicament to be delivered. Conventional10 ml drug vials contain approximately a 3-4 week supply of themedicament. The second chamber 221 may be a conventional syringe with aplunger 223. The fluid communication path 241 may be a disposablemicroneedle. The valving system 231 may be a 3-way valve in fluidcommunication with the first chamber 211, the second chamber 221 and thefluid communication path 141. Operation is similar to that of the highpressure drug delivery system of FIG. 1, except that the dose is set atthe syringe and the syringe plunger 223 is withdrawn to draw the doseinto the syringe. Additionally, a vent 251 is connected the firstchamber 211 so when medicine exits the first chamber 211, the vent 251allows air into the first chamber 211 to prevent a vacuum from beingcreated. Conventional vials are closed containers without a movingstopper. The vent 251 prevents anything but air from entering the firstchamber.

As shown in FIG. 3, the high pressure drug delivery system 300 includesa first chamber 311, a second chamber 321, a valving system 331 and afluid connection path 341. The first chamber 311 may be a conventional 3ml cartridge that stores the medicament to be delivered. Conventional 3ml cartridges hold twenty (20) doses (15 unit average). The secondchamber 321 may be a conventional syringe with a plunger 323. The fluidcommunication path 341 may be a disposable microneedle. The valvingsystem 331 may be a first check valve 333 disposed in fluidcommunication with the first chamber 311 and the second chamber 321 anda second check valve 335 in fluid communication with the second chamber231 and the fluid communication path 341. The first check valve 333 mayhave a manual override to allow for dose correction or resetting.

To use the high pressure drug delivery system 300 of FIG. 3, the userdials the dose using the thumbwheel of the cartridge so that the dosemay be viewed through the dose window. The cartridge plunger 313 is thendepressed to transfer the dose to the syringe, thereby causing thesyringe plunger 323 to rise. The first check valve 333 prevents backflowof the dose to the first chamber 311. The first check valve 333 may havea manual override to allow for dose correction or resetting. The userthen uses the syringe plunger 323 to inject the dose through the secondcheck valve 335 and through the fluid connection path 341. The valvingsystem 331 prevents the first chamber 111 from seeing the high pressureassociated with the drug delivery, thereby preventing dose inaccuracies,leakage and other problems associated with cartridges being exposed tohigh pressure.

As described above, the dose setting mechanism may set both the dose andthe prime, thereby providing a self-priming system. When the dose isset, the second chamber 321 (the syringe) is set to only accept the doseand not the prime. The syringe may include a limiter that allows thesyringe to only accept the dose amount. When the user pushes both thedose and the prime into the syringe injection chamber, the prime hasnowhere to go but out through the second check valve 335 and through thefluid connection path 341, thereby priming the high pressure deliverysystem. Alternatively, the dose may be set on the syringe side to limitthe stroke of the syringe.

As shown in FIG. 4, the high pressure drug delivery system 400 includesa first chamber 411, a second chamber 421, a valving system 431 and afluid connection path 441. The first chamber 411 may be a conventional10 ml drug vial that stores the medicament to be delivered. Conventional10 ml drug vials contain approximately a 3-4 week supply of themedicament. The second chamber 421 may be a conventional syringe with aplunger 423. The fluid communication path 441 may be a disposablemicroneedle. The valving system 431 may be a first check valve 433disposed in fluid communication with the first chamber 411 and thesecond chamber 421 and a second check valve 435 in fluid communicationwith the second chamber 431 and the fluid communication path 441. Thefirst check valve 433 may have a manual override to allow for dosecorrection or resetting. Operation is similar to that of the highpressure drug delivery system of FIG. 3, except that the dose is set atthe syringe and the syringe plunger 423 is withdrawn to draw the doseinto the syringe. Additionally, a vent 451 is connected the firstchamber 411 so when medicine exits the first chamber 411, the vent 451allows air into the first chamber 411 to prevent a vacuum from beingcreated. Conventional vials are closed containers without a movingstopper. The vent 451 prevents anything but air from entering the firstchamber.

As shown in FIGS. 2 and 4, a vial-based system may be used with the highpressure drug delivery system. For example, the vial may have a volumeof 10 ml, thereby providing approximately a 3-4 week supply of insulinto the user. Pre-filled vials are more readily available and lessexpensive than cartridges. Additionally, a plunger check valve may beused with a vial-based system.

In another exemplary embodiment of the high pressure drug deliverysystem 500 using vial-based delivery as shown in FIG. 8, the valvingsystem 531 may be a manual switch check valve disposed in fluidcommunication between the first chamber 511 (vial) and the secondchamber 521 (syringe). To operate the high pressure drug delivery system500, the user first sets the check valve to the “set dose” setting usingthe lever 533. Air is then drawn into the syringe in an amountsubstantially equivalent to the dose size. The air is then injected intothe vial. The check valve is then switched to the “inject” setting usingthe lever 533. The dose is then redrawn into the syringe, which now onlyincludes insulin. The dose may then be delivered to the user.

When the check valve is set to the “set dose” mode, the check valveprevents flow into the syringe. The check valve that is open to air thencracks open under the vacuum, thereby drawing air into the syringethrough the check valve. The drawn in air is then injected through themanual switch check valve into the vial, thereby pressurizing the vialwith that “dose of air.” When the manual switch check valve is switchedto the “inject” mode, the syringe may be reloaded with the dose, whichis now only insulin. Switching the valve to the “inject” mode reversesthe check valve orientation, i.e., the direction of flow. Both checkvalves now only allow flow out of the syringe through the fluidconnection path 541 (microneedle) so that the drug delivery may be made.

As shown in FIG. 9, for a given diameter “D” first chamber and a givendiameter “d” second chamber, the required characteristics to accomplisha high pressure drug delivery with a user input of four pounds areprovided.

In another exemplary embodiment of the present invention shown in FIGS.10-18, a high pressure drug delivery system 500 uses a vial 511 and agear pump assembly 521 to meter the doses. As shown in FIGS. 10 and 12,the diameter of the dose input 523 to the gear pump assembly 521 isgreater than the diameter of the gear pump assembly discharge 525,thereby providing a high pressure discharge. Each of the gears 531 and533 of the gear pump assembly 521 may include a deep tooth 532 and 534to provide a prime pocket, as shown in FIG. 11. The meshing of the gears531 and 533 of the gear pump assembly 521 pumps fluid by creating a voidto draw fluid into the gear teeth, carries the fluid between the teeth,and discharges the fluid with high pressure from the meshing of theteeth. Rigid gear teeth with tight tolerances allows for high pressureapplications. A conventional gear pump assembly 521 is shown in FIG. 14.

A dose is dialed with the dose screw 555 at the syringe 551 as shown inFIG. 12, which pulls up the syringe plunger 553, thereby loading thesyringe with an “air dose.” The syringe plunger 553 is then pushed downto close the syringe fill valve 571 and to force the air out of thesyringe 551 into the vial 511. Pushing down the syringe plunger 553 alsocauses the gear pump assembly 521 to rotate, thereby drawing insulin outof the vial 511 and to the fluid connection path 561, such as amicroneedle, at a high pressure. The high pressure drug delivery system500 generates a high pressure using a gear pump assembly 521 that metersin ½ unit accuracy. The valving system 571 is on the “air side” not the“insulin side” of the delivery device, as shown in FIGS. 12 and 13. Thevial 511 contains approximately a 3-4 week supply of insulin, therebyreducing the amount of waste.

In another exemplary embodiment of the high pressure drug deliverydevice 600 shown in FIG. 10, a syringe 651 that is filled with airthrough check valve 681 during dose setting, which is used to addpressure to the vial 611 as insulin is removed. After the dose is setand the user begins to inject, the air from the syringe 651 is pushedthrough a check valve 671 and into the vial 611 to prevent a vacuum frombeing formed in the vial. At the same time, the torque generated fromthe user's downward force on the syringe plunger 655 turns the gear pumpassembly 521 that draws insulin out of the vial 611 and pumps it withhigh pressure to the fluid connection path 561.

The gear pump assembly 521 allows the teeth 535 and 536 to be sized suchthat each drug volume space or pocket 537 and 538, which is the spacebetween the teeth 535 and 536, respectively, may be ¼ or ½ unit volumes,or any other volume appropriate for metering and dose accuracy, as shownin FIGS. 15 and 16. Additionally, the first pockets 532 and 534 may bedesignated as “prime pockets” sized for the volume needed to prime thehigh pressure drug delivery system 500. Alternatively, the drug volumespaces or pockets 537 and 538 do not have to be equal for each tooth 535and 536, respectively. For example, the first volumes after the primemay be smaller and then gradually increase in volume as the dose becomeslarger, as shown in FIGS. 17 and 18. This provides a variable ratecontrol while maintaining accuracy, thereby providing slower infusion atthe beginning of the injection and speeding up at the end. The mating ofthe variable rate injection with intradermal injection pressure mayreduce overall backpressures and facilitate controlling the weeping orfluid leakage form the injection site.

The vial-based delivery device allows a larger 10 ml vial to be usedinstead of the smaller 3 ml cartridge, thereby increasing the availableamount of doses and reducing the need for so many smaller cartridges. Byusing a gear pump assembly 521, the ability to provide high pressure isprovided while also accurately metering doses. The gear pump assembly521 may also provide variable rate control in connection with aconsistent input, such as a torsion spring, driving the dose. Primingmay be incorporated into the gear tooth layout by providing specificallysized teeth to hold the prime volume before the dose to ensure primingoccurs.

As shown in FIGS. 17 and 18, the high pressure drug delivery system 500according to an exemplary embodiment of the present invention may use avariable rate gear pump assembly. A variable rate is achieved byproviding smaller volumes between the first few gear teeth, and followedby larger volumes thereafter. For example, the four volumes between thefirst five gear teeth may amount to the first unit of insulin, with theremaining volumes being one unit each. The advantage of providing aslower rate of insulin flow in the beginning of the injection may leadto reduced back pressure during intradermal injection. Reduced orcontrolled back pressure may lead to more successful injections withrespect to less leakage and reduced forces required for intradermalinjection.

While exemplary embodiments have been chosen to illustrate theinvention, it will be understood by those skilled in the art thatvarious changes and modifications may be made therein without departingfrom the scope of the invention as defined in the appended claims.

The invention claimed is:
 1. A high pressure delivery system fordelivering a medicament, comprising: a first chamber for storing asupply of the medicament; a vent connected to the first chamber; asecond chamber in fluid communication with said first chamber; a fluidconnection path in fluid communication with said second chamber fordelivering the medicament, said fluid connection path not in fluidcommunication with said first chamber; and a check valve in fluidcommunication with said first and second chambers and said fluidconnection path; wherein said check valve allows a dose of themedicament to be moved from said first chamber into said second chamberwhile air enters the first chamber via the vent prior to medicationdelivery; during medication delivery, said check valve allows the dosein said second chamber to be administered through said fluid connectionpath while substantially preventing, the dose from flowing back intosaid first chamber; said check valve includes a manual override thatallows for dose correction or resetting prior to medication delivery;and said vent is independent of said check valve and said manualoverride.
 2. The high pressure delivery system for delivering amedicament according to claim 1, wherein said fluid connection pathcomprises a needle.
 3. The high pressure delivery system for deliveringa medicament according to claim 1, wherein said dose is set relative tosaid first chamber by expelling said dose from said first chamber. 4.The high pressure delivery system for delivering a medicament accordingto claim 1, wherein said dose is set relative to said second chamber byreceiving said dose in said second chamber.
 5. The high pressuredelivery system for delivering a medicament according to claim 1,wherein said check valve prevents fluid communication between said firstchamber and said fluid communication path.
 6. The high pressure deliverysystem for delivering a medicament according to claim 1, wherein duringmedicament delivery, the check valve is disposed upstream of the fluidconnection path.
 7. The high pressure delivery system for delivering amedicament according to claim 1, wherein the first chamber includes avial.
 8. The high pressure delivery system for delivering a medicamentaccording to claim 7, wherein the vial does not include a movingstopper.
 9. The high pressure delivery system for delivering amedicament according to claim 1, wherein the second chamber includes amovable plunger.